This proposed research is based upon the hypothesis that the manifestation of the intrinsic properties of vascular smooth muscle's contractile elements as responses of the intact artery are modified by the mechanical properties of the passive elements with which the contractile elements are functionally connected. The objectives of the work proposed herein are to determine a) how the interaction of connective tissue and smooth muscle in the arterial wall is manifest, b) the contribution of the various wall components to the properties of the functional wall elements, and c) how differences and/or changes in passive element properties affect this interaction. Studies will be performed on isolated cylindrical segments of canine arteries a) from different anatomical sites in the same animal, b) from animals during growth and development, and c) after partial digestion of connective tissue by elastase or collagenase. Measurements of external diameter, internal pressure and axial force will be made simultaneously and used to compute values of wall stresses and strains. Measurements will be made under conditions of norepinephrine activation and metabolic inhibition of smooth muscle. Active artery responses will be represented in terms of isometric stress development and wall constriction. Data will be analyzed in terms of three element operational (Hill) models, consisting of series and parallel elastic elements, and contractile elements. The mechanical properties of the elastic elements will be determined using quick-release procedures (series element) and from passive data (parallel element). Properties of the contractile elements will be represented by force-velocity-length relations obtained from after-loaded quick-release responses, corrected for the effects of series and parallel elasticity. The results of these various experiments will be correlated and evaluated to determine a) the relation between properties of the various functional elements and the active responses of the artery, b) the effects or changes and/or differences in artery composition on this relation, and c) the utility of the models. BIBLIOGRAPHIC REFERENCE: Cox R.H.: Determination of series elasticity in arterial smooth muscle. Am. J. Physiology V232:1977, in press.